In some situations when an application is running on a particular system within a system cluster, it is desirable to move the application to another system within the cluster. Moving an application from one system to another entails shutting down the application on the first system and starting it up on the other. Reference is made to FIG. 1, which shows a timing diagram of such an operation as sometimes currently occurs in a software environment. When it is desired for a move to take place, an order is given at time T0 by some form of application availability management software to stop the first instance of the application, shown at 100, that is present on a first system, shown at 102, and at the same time, an order is given to start up a second instance of the application, shown at 104, on the second system, shown at 106. In many situations, the shut down of the first instance of the application 100 takes place relatively quickly. However, prior to the start up of the second instance of the application 104 on the second system 106, some support resources may need to be running on the second system. Support resources are shown in FIG. 1 at 108a, 108b and 108c. In the example, shown in FIG. 1, the support resource 108a needs to be running before support resource 108b can be started up, and the support resource 108b needs to be running before the support resource 108c can be started up. Accordingly, at time T0, the order is given to start up the support resource 108a. Once the support resource 108a is running, at time T1, the start conditions are satisfied for starting up the support resource 104b and so it is started up. Once the support resource 108b is running, at time T2, the start conditions are satisfied for starting up the support resource 104c, and so it is started up. Once the support resource 108c is running, at time T3, the start conditions are satisfied for starting up the second instance of the application 102. After a start-up period, the second instance of the application 102 is itself running, at time T4.
The total time period during which the application is inaccessible was T4 minus T0, which is shown in FIG. 1 as TPmove1. The total time period TPmove1 may be inconveniently long for users waiting for the startup of the second instance for the application 104. Additionally, in some situations any of the support resources 108a, 108b and 108c can fail during their start up. This can result, for example, in the need for an alternative supporting application to be started up, or which can result, for example, in the need to start up a third instance of the application on a third system. Thus, the total time period TPmove1, could be significantly longer than that shown in FIG. 1.
As illustrated by the aforementioned scenarios, the application can suffer a significant outage during a move. It would be advantageous to reduce the time that an application is down during a move.